It's a lot different from hugging.Hugging involves arms and hands; and leaning is whole bodies moving in,leaning involves wanting and accepting.

Lucy: (to Jack) Okay, um. What do you mean by the leaning thing? You mean because he gave me flowers?
Jack: And then you *leaned*
Lucy: And then I leaned.
Jack: Yeah.
Lucy: Okay, how did I lean when I leaned?
Jack: It was a lot different from hugging. Hugging's very different. Hugging that involves arms and hands; and leaning is whole bodies moving in like this ..(leans forward suggestivley)
Jack: . Leaning involves *wanting*... and *accepting*. *Leaning*...
Joe Jr.: Hey Luce! Is this guy bothering you?
Lucy: (Laughs) No, no.
Joe Jr.: Are you sure? Because it looks like he's *leaning.*